multiboot: Check validity of mh_header_addr

I couldn't find a case where this prevents something bad from happening
that isn't already caught by other checks, but let's err on the safe
side and check that mh_header_addr is as expected.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jack Schwartz <jack.schwartz@oracle.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/hw/i386/multiboot.c b/hw/i386/multiboot.c
index 1e215bf8d3..5bc0a2cddb 100644
--- a/hw/i386/multiboot.c
+++ b/hw/i386/multiboot.c
@@ -229,6 +229,10 @@ int load_multiboot(FWCfgState *fw_cfg,
             error_report("invalid load_addr address");
             exit(1);
         }
+        if (mh_header_addr - mh_load_addr > i) {
+            error_report("invalid header_addr address");
+            exit(1);
+        }
 
         uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
         uint32_t mb_load_size = 0;